Vacuum electronics devices include devices such as field emitter arrays, vacuum tubes, electric thrusters, gyrotrons, klystrons, travelling wave tubes, thermionic converters, and the like. In vacuum electronics devices, it may be beneficial to place a conductive grid (for example, a control grid, suppressor grid, screen grid, accelerator grid, focus grid, or the like) closely adjacent to an electrode (for example, a cathode or an anode). Such a grid may use a bias voltage to control and/or modulate the flow of charged particles in the vacuum electronics device.
Integrated grids are monolithic structures which integrate the grids and the electrodes. Integrated grids are usually microfabricated by starting with a metal/insulator/metal film, and then etching apertures into the first two layers so that the bottom layer is exposed to vacuum. The top layer becomes the conductive grid and the bottom layer becomes the electrode. The insulator layer serves as a mechanical support for the grid. However, a drawback is that the maximum voltage in the conductive grid is limited due to the insulator's susceptibility to dielectric breakdown. Furthermore, because the insulator is in direct contact with the grid and the electrodes, under certain voltage bias, high leakage current may flow through the bulk of the insulator and/or on the exposed insulator surface. An example of an integrated grid is a Spindt tip array. See U.S. Pat. No. 3,755,704.
Referring to FIG. 1, an insulator layer 2 in a conventional integrated grid structure 1 may be disposed in the line of sight between a conductive grid 4 and an electrode 6 (such as, for example, an anode). In such conventional integrated grids, particles 8 (such as electrons, ions, gas molecules, adatoms, or the like) may impact the insulator layer 2. The impact of such particles 8 on the insulator layer 2 may lead to various issues such as without limitation leakage current, electrical shorting, contamination, dielectric breakdown, degradation, and/or corrosion.